How many times a day do the hands of a watch overlap? This is a recurring trick question in interviews, capable of destabilizing even the most confident candidates. While they don't necessarily expect the exact answer, recruiters mostly test your reasoning and communication skills. It is therefore important to remain Zen in order to be able to answer and convince the interviewer.
The right answer: 22 times a day
A day counts 24 hours and there are two types of watches with hands. There are on the one hand watches that do not have a second hand (being the watches with two hands) and on the other hand watches with a second hand, having three hands in total.
For the watch without second hand
With this type of watch, you have to start from the fact that the first overlap takes place at midnight. Taking into account the constant movement of the two hands and knowing that the small hand moves forward according to the movement of the large one, the other overlaps take place at the following hours:
1 hr 5 min 27 s
2 h 10 min 54 s ;
3 hrs 16 min 21 s ;
4 hr 21 min 49 s ;
5 h 27 min 16 s ;
6 hr 32 min 43 s ;
7 h 38 min 10 s ;
8 h 43 min 38 s ;
9:49:05 a.m.; 9:49:05 a.m;
10 h 54 min 32 s ;
12 hours ;
1:05:27 p.m.; 10:54:32 p.m.; 12 hours; 1:05:27 p.m;
2:10:54 p.m.; 2:10:54 p.m;
3:16:21 p.m.; 3:16:21 p.m. ;
5:27:16 p.m.; 5:27:16 p.m;
18 h 32 min 43 s ;
7:38:10 p.m.; 7:38:10 p.m;
8:43:38 p.m.; 8:43:38 p.m;
21 h 49 min 5 s ;
22 h 54 min 32 s; 22 h 54 min 32 s
In this timeline, counting the next one at midnight would be like counting an overlap twice. Therefore, the number of overlaps per day is 22.
For a watch with second hand
In constant motion, the three hands align perfectly only twice a day. At midnight and noon.
The answer is therefore not unique. Whether you answered 2 or 22, you would have given a good answer. It will be enough afterwards to justify your answer by specifying the type of watch considered. For more effect, you can always give both answers.
In case of an impasse, turn the situation to your advantage.
If during an interview you are confronted with this type of question and unfortunately you don't have the answer, don't let any form of panic or stress show through. Don't be too slow to give an answer (avoid body language that reflects a certain hesitation such as pulling the earlobe with your fingers with expressions like uh), this could work to your disadvantage.
Put forward your sense of improvisation, make sure you use well-constructed sentences with coherent reasoning. For example, you can answer the question in a humorous tone with a reference to time.
For example, you can answer "Time is not an obsession. I don't look at my watch enough to know it, because I'm never bored", or "Time passes through the hole in the hour hand". Such answers have the advantage of presenting you to the eyes of your interlocutor as someone who, although not a watchmaking engineer, is endowed with great culture.
Above all, avoid answers that would indicate a sort of "junk". Answers such as "no idea", "I never really asked myself that question", or "Impossible to say". You would give the interviewer the wrong impression, because even if you have the profile and experience required for the position, they will see you more as someone whose primary concern is not finding solutions to a given problem, or worse, someone who does not show perseverance. Another answer to the question How many times a day do the hands of a watch overlap?